1/8" roll pins are .131 before pressing into a hole. The smallest hole a 1/8" roll pin should be pressed into is a .125. Any hole smaller than .125 and the ends of the roll pin are touching and it will not compress very well. You would only press one into a .125 hole if you were dealing with a thick, solid parts. For thin material, light duty application you only need a couple thousandths of interference. The real problem is most LPK's (other than RRA) seem to have the hole in the trigger guard drilled .125 before hard anodizing, and hard anodizing has a build thickness of .001. That adds up to give you a .123 hole in the trigger guard. I have precision measured this many many many times with gauge pins. The solution is to have a #30 drill bit handy whenever you are building a lower. A #30 is .128, that will give you exactly .003 of interference, which is perfect for this application.